Saturday, 15 July 2006
148-14

Earthworm Communities in Different Soil Habitats of the Eastern Palouse Region.

Yaniria Sanchez-de Leon, Katherine Smetak, and Jodi Johnson-Maynard. Univ of Idaho, Plant, Soil and Entomological Sciences Dept, Room 242, Moscow, ID 83844-2339

The Palouse region of southeastern Washington and west central Idaho is characterized by a Mediterranean type climate, deep loess soils, and native steppe vegetation. Intense land use change has occurred in the area and as a result the Palouse is now a mosaic of agricultural fields, urban areas, Conservation Reserve Program (CRP) set-asides, forest patches, and native prairie remnants. Earthworm communities in different soil habitats have been little studied in the Palouse region. The main objective of this work was to measure and compare earthworm populations in four land use types within the region: agriculture, CRP, urban, and native prairie. We hypothesized that exotic earthworms would be dominant in disturbed sites (i.e. agriculture, CRP and urban) and native earthworms would be dominant in undisturbed sites (i.e. prairie remnants). Agricultural soils under no-till and conventional tillage management and wheat/pea/barley rotations were sampled annually between 2001 and 2003. Urban sites were characterized as old residential (more than 75 years old), young residential (less than 10 years old) and urban parks (more than 75 years old). Earthworms were sampled in the urban areas during 2004. In CRP lands and adjacent prairie remnants earthworms were sampled once a year from 2003 to 2005. All sites were sampled during spring and early summer months (April through June). European earthworms were predominant at all sites, however the dominant species differed depending on land use. The European earthworm Aporrectodea trapezoides was dominant in agricultural fields, CRP lands, and prairie remnants. However, Lumbricus terrestris was dominant in urban areas. Only one native earthworm (Driloleirus americanus) was found in a prairie remnant. Overall mean earthworm density in no-till barley, pea and wheat crops was 140, 146 and 74 individuals m-2, respectively. However, under conventional tillage with the same crops, earthworm densities were 38, 35 and 26 individuals m-2, respectively. Mean earthworm density for young residential sites was 41 individuals m-2, earthworm density at old residential sites was 138, and urban parks had the highest density with 418 individuals m-2. Mean earthworm density was 83 individuals m-2 in CRP sites and 49 individuals m-2 in prairie remnants. Contrary to our hypothesis, the preliminary data showed that exotic European earthworms dominate both native and disturbed soil habitats. Native earthworms were present, in very low densities, in one of the five native prairie remnants sampled. Exotic earthworm densities were higher in sites with lower disturbance frequency (i.e. no-till) or with older residential sites with more intense management (i.e. urban parks). Our data suggest that earthworm communities across the Palouse are influenced by land use and the level of management intensity within a land use. Intensively managed (regularly fertilized and irrigated) urban parks appear to support greater earthworm density than do relatively undisturbed prairie and CRP.

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